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Herbal products are widely used in cancer patients via co−administration with chemotherapy. Previous studies have demonstrated that pharmacokinetic interactions between herbs and anticancer drugs exist due to inhibition of drug−metabolizing enzymes, particularly cytochrome P450s (CYPs). The aim of this study was to determine the inhibitory effects of Andrographis paniculata, Curcuma zedoaria, Ganoderma lucidum, Murdannia loriformis and Ventilago denticulata extracts on the metabolism of gefitinib, lapatinib and sorafenib. The activities of CYP3A in human liver microsome on the metabolism of gefitinib, lapatinib and sorafenib in the absence and presence of Thai herbal extracts were assayed using high-performance liquid chromatography analysis. Curcuma zedoaria extract potently inhibited CYP3A−mediated lapatinib and sorafenib metabolism with IC50 values of 4.18 ± 3.20 and 7.59 ± 1.23 μg/mL, respectively, while the metabolism of gefitinib was strongly inhibited by Murdannia loriformis and Ventilago denticulata extracts with IC50 values of 7.53 ± 2.87 and 7.06 ± 1.23 μg/mL, respectively. Andrographis paniculata and Ganoderma lucidum extracts had less effect on the metabolism of the tested anticancers (IC50 values >10 μg/mL). In addition, kinetic analysis of the ability of Curcuma zedoaria extract to inhibit CYP3A-mediated metabolism of anticancer drugs was best described by the noncompetitive and competitive inhibition models with Ki values of 20.08 and 11.55 μg/mL for the metabolism of gefitinib and sorafenib, respectively. The present study demonstrated that there were potential pharmacokinetic interactions between tyrosine kinase inhibitors and herbal extracts.